my focus seems to idle too slow , the dash starts to rattle etc as its around 500rpm

is this something i can alter? just needs a few more revs

ive already cleaned the isv and no change

 

Have you looked at the throttle body recently? If so does the flap open much when revved? It would be worth cleaning it out with something that won't strip off the protective coating.

Check the condition of the spark plugs and the wells for rust also.

 

recent genuine ford plugs and i have looked at the tb , seems clean enough

 

How old is the battery? what condition are the terminals in any signs of corrosion? It doesn't take much for a battery to act up.

 

new around xmas , proper top of the range one too , terminals are good but i guess i should check the voltage when running

any idea what a healthy one should idle at?